Certain Transfers of Financial Assets and Variable Interest Entities - Additional Information (Detail) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Loans and Leases Receivable, Gain (Loss) on Sales, Net		$ 45		$ 45
Loans and Leases Receivable, Net Amount		154,908		154,908		$ 150,224
Total liabilities		196,426		196,426		191,263
Long-term Debt	[1]	20,200		20,200		15,072
Debt Securities, Trading, and Equity Securities, FV-NI	[2]	6,610		6,610		5,506
Investment Tax Credit			$ 20
Amortization of Intangible Assets	[3]			7	$ 11
Variable Interest Entity, Not Primary Beneficiary [Member]
Investment Tax Credit				38	38
Amortization of Intangible Assets		17	16	32	31
Variable Interest Entity, Primary Beneficiary [Member]
Long-term Debt		149		149		161
Residential Mortgage [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Loans and Leases Receivable, Gain (Loss) on Sales, Net		67	19	116	7
Commercial and Corporate Loans [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Loans and Leases Receivable, Gain (Loss) on Sales, Net		11	$ 5	18	$ 14
Student Loans [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Loans and Leases Receivable, Net Amount		153		153		165
Long-term Debt		$ 149		$ 149		$ 161
Student Loans [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Maximum [Member]
Government Guarantee Percent		98.00%		98.00%		98.00%
Total Return Swap [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Derivative Asset, Notional Amount		$ 2,400		$ 2,400		$ 2,000
Debt Securities, Trading, and Equity Securities, FV-NI		$ 2,400		$ 2,400		$ 2,000
Death, Disability, Bankruptcy [Member] | Student Loans [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Maximum [Member]
Government Guarantee Percent		100.00%		100.00%

[1] Includes debt of consolidated VIEs of $149 million and $161 million at June 30, 2019 and December 31, 2018, respectively.

[2] Includes trading securities pledged as collateral where counterparties have the right to sell or repledge the collateral of $1,214 million and $1,442 million at June 30, 2019 and December 31, 2018, respectively.

[3] Does not include expense associated with community development investments. See Note 11, “Certain Transfers of Financial Assets and Variable Interest Entities,” for additional information.